Conversion of hydrocarbons



Patented Sept. 18, 1945 2,384,877 CONVERSION or nrnaooannons Richmond T. Bell and Carlisle M. Thacker, Highland Park, Ill., assignors to The Pure Oil Company, Chicago, 11]., a corporation of Ohio No Drawing. Application January 10, 1944, Serial No. 517,702

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This invention relates to the conversion of hydrocarbons and more particularly to the conversion of higher boiling hydrocarbons into lower boiling hydrocarbons and/or into hydrocarbons more unsaturated than the hydrocarbons subjected to conversion.

One of the objects of the invention is to provide a method for converting hydrocarbons into lower boiling hydrocarbons.

Another object of the invention is to provide a. method for converting hydrocarbons into more unsaturated hydrocarbons;

Still another object of the invention is to provide a method for preparing high octane motor fuel from hydrocarbon oils. Further objects themselves from the following description.

We have discovered that the conversion of liquid hydrocarbons, particularly those hydrocarbons boiling above the boiling range of gasoline, such as gas oil, can be cracked to yield gasoline of considerably higher octane value than is obtainable when the oil is subjected to purely thermal cracking, if a small amount of an ester of an oxygen-containing acid of phosphorus is mixed with the oil undergoing cracking. Esters of oxygen-containing acids of phosphorus which we have found to be particularly effective are the octyl esters, such as di-octyl acid pyrophosphate, trioctyl acid tetrapolyphosphate and penta-octyi acid tripolyphosphate.

The ester may be added to the charging stock before charging it to the heating and conversion zones or it may be injected directly into the conversion zone, preferably in the form of a solution in a solvent such as petroleum naphtha. The esters are effective as cracking accelerators or sensitizers in amounts as low as .05% by weight of the charging stock. Amounts between .05% and 5% .by weight may be used effectively, although larger amounts may be used if desired. We prefer not to use amounts in excess of 3% by weight since amounts below 3% by weight provide satisfactory acceleration of the cracking reaction without causing the presence of objectionof the invention will manifest able amounts of esters or decomposition products thereof in the product of the reaction. Our experiments indicate that satisfactory results can be obtained when the sensitizer is used in amounts of 1% or less. v

The alkyl esters of-oxygen-containing acids of phosphorus are useful in conventional thermal cracking processes at either atmospheric, subatmospheric or superatmospheric pressure. Cracking of the oil may be carried out at temperatures ranging from approximately 350 C. to 600 C. although we prefer to crack at temperatures of 500 C. or less since the sensitizers appear to function most efiectively within the lower cracking temperature range.

The sensitizer may be mixed directly with the oil to be charged or may be dissolved in a suitable solvent such as hydrocarbons boiling within the gasoline boiling range and the solution mixed with the oil to be charged or injected directly into the reaction zone.

Inorder to demonstrate the efl'ectiveness of the alkyl esters of oxygen-containing acids of phosphorus, as sensitizers in the conversion of hydrocarbons, a number of runs were made in which gas oil from a Pennsylvania grade crude was subjected to cracking in a laboratory tube and drum apparatus at 500 pounds per square inch and at temperatures of 475 C. and at 500 C. Some runs weremade without any sensitizer or .,catalyst in order to furnish a basis of comparison with the runs in which sensitizer was used. In

some runs the sensitizer was mixed directly with the gas oil charged to the cracking apparatus while in other runs the sensitizer was dissolved in V. M. and P. naphtha. and the naphtha solution was mixed with gas oil prior to charging it to the cracking apparatus. In certain runs. a small amount of codimer-the product resulting from the polymerization by means of solid phosphoric acid catalyst of the C4 cut from jgases produced in the cracking of petroleum oil--was mixed with the oil subjected to conversion. The results of the various runs are reported in the following table:

Product yields. per cent by volume or Grams per gal.

charging stock oi charge- Per cent Pres. A S T M Bun Charge Temp. unsatumm a Q per Sensitizer 00 F ot rates in I octane sq. in. I. P. I. B. P 400 Residue C and C and gonna No. 1 F. 400 F 650 F. above lighter heavier g E. P. E. P. gasgas oil 650 F. gas gas oline 668-B. l 997 475 500 *3. 5 16. 6 71. 3 7 65. 88 31. 16 41 51. 4 665.--.. 1 1.000 475 500 Di-octyl acid pyio- 3.2 14.8 75.8 5.8 48. 37 20.41 43 60.4

phosphate. 606..-" 1 1.001 475 500 Tri-octyl acid tetra- 2. 0 16.0 72. 7 8.0 56. 69 22.90 46 62.1

polyphos hate. 007..." 1 0.999 475 500 lenta-octy acid tri- 3. 8 10.4 71.3 8.0 60.22 25.53 46 62.2

polyphosphate. 682..." 0. 997 475 500 2.7 18. 1 70.7 5.3 91.87 47.02 44 59. 2 679"-.. 1 1. 011 475 500 Di-(lilctylhagid pyro- 2. 2 19.0 72.3 4. 6 70.01 39. 80 48 63. 5

. p osp a e. 680..." 1 1. 006 475 500 Tri-octyl acid tetra- 2. 4 18. 8 68. 5 7. 6 84. 87 45. 70 51 6 1.2

polyphosphate. 68l-B 1 1. 004 475 500 Pente-octy acid tl'i- 1. 0 17- 3 72- 4 6. 2 71. 70 37. 82 65. 1

polyphosphate. 687-.." 1 0. 869 500 500 4. 3 33. 3 48- 5 5. 1 202.0 92. 91 33 54.1 688-3.. 1 0. 872 500 500 Di-gctylhagd pyro- 3. 2 33. 2 45. 1 ll. 2 190. 72 B4. 26 33 56. 5

p osp a 689 9 0. 868 500 500 Penta-octyl acid tl'i- 2. 8 33. 7 51. 1 4. 2 207. 14 91. 47 37 58. 6

polyphosphate. 591".-. a 1.008 475 500 .6 0- 59.6 4. 8 90.33 43.84 34 47.5 092.--" 6 1. 008 475 500 Penta-octyl acid 131- 2. 8 2S. 4 61. 0 5. 0 83. 50 46. 16 36 55. 9

poly phosphate.

1 Gas oil. 3 Figures are for gas oil charged. l Charge consisted of .865 gaL/hr.

6 Charge consisted 01 .857 gaL/hr.

In runs 665, 566, 657, 579, 680 and 681-13, 1% by weight of the sensitizer was mixed with the gas oil for about an hour in a glass stirring vessel and the resulting gas oil was decanted from the vessel. It was observed that a separate layer remained on the bottom of the vessel indicating that the sensitizer only partially dissolved in the gas oil. In runs 587, 688-3, 089 and 692, the sensitizer was dissolved in V. M. and P. naphtha and the solution was mixed with the gasv oil or with the gas oil-codimer blend to give a resultant charging stock which analysis showed as containing about 0.5% by weight of sensitizer.

Referring to runs 668-3 to 66'? inclusive, it will be apparent that without materially affecting the yield of gasoline produced by cracking gas oil at 475 C. and under 500 pounds per square inch pressure, the A. S. T. M. octane number was increased from 51.4 without sensitizer to as high as 62.2 using penta-octyl acid tripolyphosphate. In the series of runs from 682 to 681-8 a. maximum increase of approximately 6 octane numbers was obtained. In runs 687, 688-8, and 689, which were made at a temperature of 500 C., the improvement in octane is not so noticeable as it is at 475 C. Runs 691 and 692 were made with a blend of gas oil and codimer in the ratio of 95 to 5 by volume in order to determine if the codimer would have any effect on the reaction. The use of penta-octyl acid tripolyphosphate produced a gasoline having an octane number more than 8 points above that produced without sensitizer. This result is the more unexpected since a similar mixture containing no codimer, that is, one

. containing only gas oil, V. M. 8: P. naphtha and penta-octyl acid tripolyphosphate, produced substantially no increase in octane number over that which can be obtained from the same mixture of gas oil and naphtha. without the sensitizer.

Not only are the esters useful in the conversion of liquid hydrocarbons such as gas oil and higher boiling hydrocarbons to gasoline boilin hydrocarbons of high anti-knock value, but they are useful in promoting reaction between low boiling normal and iso-olefins such as butenes, pentene's and octenes, and high boiling hydrocar- In addition 0.143 gaL/hr. of V. M. & P. naphtha having A. S. '1. M. octane No. of 24.1 was charged. of :5 blend oi gas oil and co-dimer and 0.143 of 95:5 blend oi gas oil and co-duner and 0.141 gaL/hr. of V. M. & P. naphtha.

gaL/hr. or V. M. & P. naphtha.

bons under cracking conditions of temperature and pressure, particularly under super-atmospheric pressures of the order or 500 pounds per square inch or higher.

Neutral or acid, mono or poly-alkyl or aryl derivatives of monoor poly-phosphoric acids, phosphorous acids, phcsphinic acids, and phoephonicacids or mixtures thereof, are useful in our invention.

Our invention is useful in connection with conventional type thermal cracking operations without the necessity of modifying the operation or apparatus except to provide means for introducing the sensitizer. The invention may also be used in connection with known types of solid catalytic cracking operations.

It is claimed:

1. The method of converting higher boiling crude mineral oil fractions into hydrocarbons boiling within the gasoline range comprising subjecting said fractions to cracking at temperatures of approximately 350-600" C. in the presence of a small amount, not in excess of 5% by weight of an alkyl ester of an oxygen-containing acid of phosphorus.

2. The method in accordance with claim 1 in which the cracking temperature is not substantially above 500 C.

'3. The method in accordance with claim 1 in which the ester is an octyl ester of an oxygencontaining acid of phosphorus.

4. The method in accordance with claim 1 in which the ester is di-octyl acid pyrophosphaie.

5. The method in accordance with claim 1 in which the ester is tri-octyl acid tetrapolyphosphate.

6. The method in accordance with claim 1 in which the ester is penta-octyl acid tripolyphosphate.

7. The method of preparing gasoline from crude mineral oil fractions or higher boiling range than gasoline comprising subjecting said fractions to cracking at temperatures of approximately 350- 500 C. in the presence of approximately .05 to 3% by weight or an ester or an oxygen-containing acid of phosphorus.

8. The method in accordance with claim 7 in crude mineral oil fractions of higher boiling range which the ester is an Octyl ester of an oxygenthan gasoline which comprises subjecting said containing acid 01' phosphorus; fractions to conversion at temperatures of ap- 9. The method in accordance with claim 7 in proximately BED-500 C'. in the presence of diwhich the ester is 10. The method which the ester is phate.

11. The method in accordance which the ester phate.

di-Octyl acid pyrophosphate. in accordance with claim 7 in tri-octyl acid tetrapolyphoswith claim 7 in is penta-octyl acid tripolyphosoxygen-containing phosphoric acid. I

13. Method in accordance with claim 12 in 14. Method in accordance which the ester is an octyl ester oi. an oxygencontaining phosphoric acid.

15. The method of preparing gasoline from mineral isobutyienes and in the presence of approximately .05 to 3% by weight of an ester selected from the acid pyrophosphate,

octyl acid tri-polyphosphate.

16. The method 01. cracking higher boiling crude polyphosphate.

RICHMOND T. BELL. CARLISLE M.- TRACKER. 

